A fuel injector is described in German Patent No. DE 38 25 134 A1 which includes an electromagnetic actuating element having a solenoid, an internal pole, and an external magnetic circuit component, and a movable valve closing member which cooperates with a valve seat associated with a valve seat member. The injector is enclosed by a plastic extrusion molding, which extends primarily in the axial direction and encloses the connector which acts as the internal pole, and the solenoid. Ferromagnetic fillers which conduct magnetic field lines are introduced into the plastic casing, at least in the area enclosing the solenoid. In this regard, the fillers enclose the solenoid in the peripheral direction. The fillers are fine-grained crushed particles of metals having soft magnetic properties. The small metal particles which are magnetically embedded in the plastic have a more or less globular shape, and are individually magnetically isolated and therefore have no metallic contact with one another, so that no effective magnetic field forms. However, the positive aspect of a very high electrical resistance which results is offset by an extremely high magnetic resistance which is reflected in a considerable loss of power, and which thus determines the overall unfavorable functional properties.
In addition, a fuel injector is described in German Patent No. DE 103 32 348 A1 has a relatively compact design. In this valve, the magnetic circuit is formed by a solenoid, a fixed internal pole, a movable armature, and an external magnetic circuit component in the form of a magnet pot. For a slim, compact design of the valve, multiple thin-walled valve sleeves are used which are utilized as a connector as well as a valve seat support and guide section for the armature. The thin-walled nonmagnetic sleeve extending within the magnetic circuit forms an air gap, via which the magnetic field lines pass from the external magnetic circuit component to the armature and the internal pole. A fuel injector having a comparable design is also illustrated in FIG. 1, and is explained in greater detail below for better understanding of the present invention.
Furthermore, a fuel injector is described in Japanese Patent Application No. JP 2002-48031 A which likewise is characterized by a thin-walled sleeve approach, the deep-drawn valve sleeve extending over the entire length of the valve and having a magnetic separation point in the magnetic circuit area in which the otherwise martensitic structure is interrupted. This nonmagnetic intermediate section is situated at the level of the area of the working air gap between the armature and the internal pole, and in relation to the solenoid in such a way that the most effective magnetic circuit possible is provided. Such a magnetic separation is also used to increase the dynamic flow range (DFR) compared to the conventional valves having conventional electromagnetic circuits. As a result, however, such designs entail significant added manufacturing costs. In addition, introducing such a magnetic separation having a nonmagnetic sleeve section results in a different geometric configuration compared to valves without a magnetic separation.